As near as I can tell, this only happens when using the Properties Bar. Right-clicking on the image and clicking Edit Animation works fine, Right-clicking on image under Projects Bar also works correctly.

As I don't have another computer to test this with, I can't verify whether this problem is limited to my particular configuration or is more general in nature.

Well, here I am inserting a Sprite object in layout, with right mouse click, them I choose some images, each for a diferent frame, and close the Image Editor. When I try to edit the Sprite, C2 crashes.